Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.77	7.299%	$137.0959	$137.10	$137.10	$137.10
Purchase #2	$141.26	4.740%	$147.9557	$147.96	$147.95	$148.00
Purchase #3	$180.34	6.308%	$191.7158	$191.72	$191.70	$191.70
Purchase #4	$173.98	6.411%	$185.1339	$185.13	$185.15	$185.10
Purchase #5	$164.38	13.390%	$186.3905	$186.39	$186.40	$186.40
Purchase #6	$94.62	4.131%	$98.5288	$98.53	$98.55	$98.50
Purchase #7	$52.27	12.804%	$58.9627	$58.96	$58.95	$59.00
7 purchase totals =	$934.62		$1,005.7833	$1,005.79	$1,005.80	$1,005.80